At NPR, science journalist Erik Vance has insights into the fear underlying the bogus theory. He discusses "nocebos," which happen something unhealthy happens to a body, solely based on the person's belief.
Scientists have found that nocebos are easier to create than placebos, and last longer. So fear is more powerful in the body than hope. Saying "fear is a powerful thing" is a little like saying "money can come in handy" – it kind of undersells it. Fear is the number one tool for selling newspapers, insurance, snake-oil medicine and Swedish cars. Sometimes that's a good thing and sometimes it's not. It's what kept our ancestors alive for millions of years and its history's favorite way of selling political ideology.
So it's not surprising that fear forces people to accept some strange ideas about medicine. The most tragic and extreme of these are cancer patients so terrified of modern cancer therapies that they turn towards more "natural" solutions and shun proven treatments that could have saved their lives.
I would gladly suffer a few rounds of chemotherapy to prevent harm from coming to my child. The bottom line is that what happens to me when I go in for my kid's shots has nothing to do with vaccines or mercury or thimerosal or any science whatsoever. It's about fear and a loss of control.
Maybe I've done one too many stories on autism and crossed some kind of threshold. That's how I ended up sweating when in the doctor's office again two weeks ago, waiting for the 18-month vaccination that would protect him from diphtheria, meningitis, whooping cough and tetanus. Here I was again, deeply ashamed yet still wondering if we should put off the shot until it was "safe."